1. Field of the Invention
The invention relates to an apparatus and a method for determining image region. More particularly, it relates to an apparatus and a method for determining that a target position of the image signal is included in either a motion region or a still region, and an apparatus and a method for processing an image signal.
2. Description of Related Art
An interlace-scheme image signal (interlaced signal) is employed in various image signals used in a television apparatus, a video apparatus and the like. A progressive-scheme image signal (progressive signal), on the other hands, is employed in image signals used in a computer. Thus, for example, in order to display images for the computer and the television on a computer display screen, the interlaced signal is converted into the progressive signal.
Since the interlaced signal constitutes a signal of one frame in which signals of lines are arranged one after the other as signals of odd field and even field, a flicker noise occurs if a fine horizontal line stays in an image. No flicker noise, however, occurs in the progressive signal along which a fine image is displayed even if a fine horizontal line stays in an image. In a recent case, a home-use television apparatus may convert the interlaced signals into the progressive signals therein and displays an image according to the progressive scheme.
According to the interlaced signal, one frame is composed of two fields of odd and even in which line signals are shifted to each other at intervals of one line, as shown in FIG. 1. If a conversion of such the interlaced signal into the progressive signal, namely, a so-called interlace-progressive (IP) conversion is performed, interpolation data (pixel data) is created on each line that includes no pixel data.
In this case, as shown in FIG. 2, motion detection processing is generally performed so that an image signal is divided into a motion region and a still region. In the motion region, the interpolation data is created from items of the pixel data, a1 and a2, of back-and-forth lines within the same field. In the still region, the interpolation data is created from items of the pixel data, b1 and b2, of the lines similar to each other within the back-and-forth fields.
Conventionally, relative to the motion detection processing in the IP conversion, for example, when an interpolation pixel position P is positioned in a field that precedes a current field by one field, as shown in FIG. 2, an absolute value of the difference data between pixel data “e” of a pixel position in the current field that corresponds to the interpolation pixel position P and pixel data “a” of a pixel position in a field that precedes the current field by two fields (or one frame) has been obtained as frame motion information (frame motion information for a target field). This absolute value of the difference data has been compared with a threshold value so that it can be determined that the corresponding interpolation pixel position P is included in either a motion region or a still region.
In a case where it is determined that the corresponding interpolated pixel position P is included in either a motion region or a still region by using only the frame motion information of the target field as described above, it may be accidentally determined that it is included in the still region, not the motion region, so that the data completely different therefrom is interpolated.
It has been proposed to store signals of various fields in the interlaced signal and perform the determination using not only the frame motion information of the target field but also the frame motion information of the field that precedes the target field by one field etc. to increase its determining accuracy.
According to such the determination using not only the frame motion information of the target field but also the frame motion information of the field that precedes the target field by one field etc., however, it is necessary to store signals of various fields in the interlaced signal. This causes memory capacity in storage device that is installed to be more increased, thus to enlarge a circuit scale.
The present invention alleviates the problems as mentioned above. It is an object of the present invention to provide an apparatus and a method for determining image region, and the like by which determining accuracy of determining that a target pixel position is included in either a motion region or a still region is increased with memory capacity in storage device that is installed being prevented from being vastly increased.